Electronic control for filament wrapping machines



April 29, 1952 A. M. DEXTER, JR 2,594,741

ELECTRONIC CONTROL FOR FILAMENT WRAPPING MACHINES Filed Feb. 20, 1948INVENTOR.

AFOR/VEY Patented Apr. 29, 1952 ELECTRONIC CONTROL FOR FILAMENT WRAPPINGMACHINES Albert M. Dexter, Jr., Farmington, Conn., as-

signor to Niles-Bement-Pond Company, West Hartford, Conn., a corporationof New Jersey Application February 20, 1948, Serial No. 9,887

3 Claims. (01. 153-67) This invention relates to winding machines andmoreiparticularly to a winding machine for tungsten wire in which a finefilament of tungsten is continuously wrapped about a core of wire ofsmall diameter such as of steel while the wire forming the core isadvanced at a uniform rate and maintained under tension.

An object of the invention is to promptly indicate breakage of thefilament as it is being wrapped so that the machine may be promptly andautomatically stopped as soon as a breakage occurs.

A feature of importance of the invention is that 'thebreakage indicatorforming the present invention requires no mechanical connection to thewinding mechanism but depends upon light flashes reflected from a mirrorrotated with the wrapping mechanism falling periodically on aphotoelectric tube. By means of an electronic circuit; within which thephotoelectric tube is in cluded, constant light flashes, or no light,falling on the photoelectric tube as the wrappingmechanism rotatesmaintain a stop motion device relay energized to open the main circuitcontacts for the machine and stop its operation. Variable flashesoccurring periodically during normal operation 'serve to deenergize therelay coil and maintain the main circuit contacts for the machineclosed.

In forming tungsten filaments for high and low wattage light bulbs, itis the usual custom to wrap the filament around a mandrel Or core ofsteel wire, the steel wire being continuously advanced under-tensionduring the wrapping operation so that successive convolutions of thefilament along the core will be equally spaced. After wrappingthefilament the steel core is dissolved in an acid bath whicheffectively removes the steel and leaves the helically wound filamentready for outting into proper lengths for assembly within the bulb.

As the filament is extremely fine, it is very difficult for the operatorto determine when a break occurs in the filament duringthe Winding orwrapping operation. Continued operation of the machine after breakage ofthe filament is wasteful. It is therefore a desirable feature of theinvention to stop operation promptly when the filament breaks, andwithout the addition of mechanism increasing the tension on thefilament.

To effect this stoppage advantage is taken of the difference in speed ofthe guide member for the filament and the filament carrying spoolrotated with the guide member. The rotation of the spool is at adifferent and slightly increased speed from that of the guide member byreason of the unwinding of the filament from the spool. After a breakoccurs in the filament the spool will rotate with the guide carryingmember and at the same speed.

During normal operation of the wrapping mechanism due to the differencein speedof rotation of the guide member and spool, a mirror rotatingwith the guide member is periodically exposed to a light source throughan opening in a member rotating with the spool. Reflected flashes fromthe mirror fall on a photoelectric tube and render this tube momentarilyconducting to pass current through an electronic circuit. These flasheswill vary in intensity due to the mirror slowly passing the opening, theflashes first increasing and then decreasing. After a break in thefilament the spool and guide member will rotate at the same speed sothat there will be equally timed flashes of equal intensity With eachrevolution of the guide member or if the mirror is concealed there willbe no flashes whatever. This is due to the relative positions of themirror and opening remaining unchanged. If the break occurs when theopening is above the mirror there will be a continuous series of flashesof equal intensity and at equal intervals, one with each rotation of theguide member and spool. If the break occurs when the mirror is concealedby the flange, there will be no light flashes at all. This will beobvious by an inspection of Fig. 2 of the drawing. By the electroniccircuit including the photoelectric tube the relay operating the stopmotion is not affected by the periodic varying se;- ries of flashes ofdifferent intensity but is caused to be operated and open the maincircuit for the machine by equal flashes equally timed or by no flashesat all falling on the tube. I

It is therefore a primary object of the invention to provide anelectronic circuit responsive to flashes of difierent types falling on aphotoelectric tube included Within the circuit.

In the accompanying drawing annexed hereto and forming a part of thisspecification, I have shown the invention embodied in a simple form offilament wrapping device but it will be understood that the inventioncan be otherwise embodied and that the drawing is not to be construed asdefining or limiting the cope of the in vention, the claims appended tothis specification beingrelied upon for that purpose.

In the drawing:

Figure l is a side elevation in section showing the principal parts of asimple filament wrapping machine.

Fig. 2 is a front elevation in section taken on the line 22 of Fig. 1,and

Fig. 3 is a diagram showing a preferred circuit for controlling a motoroperating relay for the machine.

In the above mentioned drawing there has been shown but one embodimentof the invention which is now deemed preferable, but it is to beunderstood that changes and modifications may be made within the scopeof the appended claims without departing from the spirit of theinvention.

In Fig. 1 are shown the operative parts only of a winding machine whichmay have the stop motion relay controlling circuit forming the presentinvention. The rotating member includes a hollow shaft It and arm {2.The base for supporting this member and its rotating means are notshown, the rotating member being shown extending from a fixed member Iwhich may be attached to a suitable base. The shaft It supports a spoolto freely rotatable on the shaft on which is wound the filament 18. Thearm 12 supports guides 20 in the form of rolls over which the filament18 passes from its spool H to the wire 22 around which it is beingwrapped.

The shaft is supporting the arm I2 is hollow and the steel wire for thecore 22 is advanced by means (not shown) axially through the shaft, andafter being wrapped by the filament I8 is wound upon a suitable drum 24which may be rotated at a uniform speed by any appropriate means. Thespool I6 is freely rotatable on its supporting shaft is so that it mayrotate relatively to as well as with the shaft while the shaft and arm52 are rotated to permit the filament I8 to unwind while the spool isrotated with the guiding member 12.

As shown in Fig. 1 the arm forming the guiding member :2 is keyeddirectly to the shaft and has mounted thereon a disc 26 .on theperiphery of which is mounted a small mirror 28. The spool it on one ofits faces is provided with a flanged member 30 fixed to the spool forrotation therewith, there being an opening 32 in the flange 3G alignedwith the mirror 28.

From the above description it will be seen that during rotation of theshaft Ill andspool It at different speeds the mirror 23 will be directlybelow the opening 32 in the flange 30 after a number of revolutions ofthe shaft It). Just before and after the mirror 28 is directly below theopening 32 for several revolutions, the mirror 28 will be partiallybelow the opening. These phases increase as the mirror 28 slowly movestoward the position directly below the opening and then decrease as themirror moves away from the opening. In the event of a breakage of thefilament the spool l6 and shaft IE] will rotate together at the samespeed and the relative positions of the mirror 28 and opening 32 willnot change. The mirror 28 may be visible below the opening 32, partiallyvisible, or completely out of sight by being hidden by the flange 3B.

Adjacent the spool 16 and shaft H! is a source of light 34 such as asmall light bulb. A lens 36 is preferably mounted between the bulb andmirror 23 so that the light rays may converge upon the flange 38. Whenthe mirror 28 is visible below the opening 32 in the flange, light fromthe bulb 34 will be reflected to a photoelectric tube 38 positionedadjacent the light source 34. The reflected flashes of light falling onthe photoelectric tube 38 will increase as the mirror 28 slowly comesinto a position below the opening 32 and will then decrease as themirror passes the opening. The passage of the arm 12 at each revolutiondoes not produce any interruption of these light flashes for the reasonthat the mirror 23 is angularly'disposed relative to the position of thearm 12.

To actuate a stop motion or motor control- 1 ling relay 4!! by means ofthe flashes of reflected light from the mirror 28 to the photoelectrictube 38 the following circuits have been devised, the diagram for thecircuit being indicated in Fig. 30f the drawing.

These circuits control energizing of relay Ml opening and closing thecontacts of a motor circuit for operating the machine. With the relay 40energized the motor circuit contacts are opened and the machine is thusstopped. So long as the coil 'of relay 49 is not energized the motorcircuit contacts are closed to continue the normal operation of themachine. The function of the circuits shown in Fig. 3 is to energize the.coil of relay .159 as soon as a break in the filament 18 occurs, and tomaintain the coil of relay 40 deenergized during normal operation of themachine.

T1 is a power transformer connected as an auto-transformer with primaryand secondary connected series windings. The first section of tube V1 isa diode rectifier. Following the current from one side of the lineindicated at A. C., it flows to the plate of diode of D1 (which forms apart of tube V1) through diode D1, to the cathode of D1, throughresistances R3, R2 R1; and potentiometer P1. and back to the end oftransformer secondary 42. Due to the half wave rectification action oftube D1, no current flows through this tube on alternate halfcycles. Apulsating uni-directional current therefore'flows through tube D1, anddue to the filtering action of condensers C1, C2 and resistance Rs. 2..steadyD. C. voltage appears across the network consisting ofresistances R2, R1, and potentiometer P1, the polarity of which isindicated in ,Fig. 3. This voltage may be called the 13 voltage supply.

T2 an audio coupling transformer with one end of its primary connectedto the terminal of the B voltage supply and the other end connected tothe plate of the second, or triode', section of tube V1. The cathodeofthe triode section of t be V1.13 connected t t e s i r of pot no eter P1n th B vol a e s pp y n w rk. Condenser Q3 forms a by-pass from thecathode of t e tri de ion f tu V1 to the m us end of B voltage supplynetwork to prevent degeneration in the cathode circuit as is thepractice in amplifying stages. The grid of the triode section of tube V1is connected through resistance R4. to the minus end of the B voltagesupply. It will be seen, therefore, that the triode section of tube V1is biased to the extent of the voltage from the slider on potentiometerP1 to 3 minus, and this slider should be adjusted until the triodesection of tube -V1 is just drawing current, that is, not quite tocut-off.

Photoelectric tube 38 referred to above is connected between grid oftriode in tube V1 and a positive tap on thenetwork formed by resistancesPsalm, and potentiometer P1. When this photoelectric tube 38 isilluminated; it becomes more conducting, and the current in flowing fromthe tap on the B voltage network through photoelectric tube 38, throughresistance R4 to the minus end of B voltage network, makes the grid lessnegative;.in other words, the triode D1 is no'longer biased negatively.Current flows from the plate of the triode section of tube V1 to thecathode, therefore, whenever the photoelectric tube 38 isv illuminated.

At this point it is well toconsider the function of the-rotating mirror28, which is on the disc 26 attached to the shaft 0, and the flange 30with the opening 32 which is attached to the spool Hi. If the mirror 28and the flange 30 are travelling at the same speed (a condition whichexists only when the tungsten filament has been broken), one of twoconditions can take place, either the mirror 28 will be totally orpartially in register with the opening 32, in which case a flash oflight will strike the photoelectric tube 38 with every revolution, oralternatively the mirror 28 will be obscured completely by the flange 30and no flashes of light whatsoever will reach the photoelectric tube 38.In any case, the photoelectric tube 38 will receive either constantflashes of light or no light at all.

Consider now the condition where the tungsten filament l8 has not beenbroken and the machine is operating normally. The mirror 28 and theflange 30 will not be travelling at the same speed, the flange will betravelling at a higher speed'due to the spools paying-off of thetungsten filament. Flashes of light will therefore reach the phototube38, but these flashes will not allbe of the same intensity. A beat willoccur at a frequency equal to the difference in speed of the mirror 28and flange opening 32, as for example, the mirror 28 one time aroundwill be obscured by the flange 3B; the next time the opening will justslightly uncover the mirror allowing a very weak flash to strike thephototube; each successive time around the opening will uncover more ofthe mirror, passing a slightly stronger flash, and so on until theentire mirror 28 is reflecting light to the photoelectric tube 33. Theopening 32 will then progressively advance so that with each revolutionless and less of the mirror 28 will be visible to the photoelectric tube38, until again it is totally obscured by the flange 30. This heat will,of course, be at a low frequency compared to the speed of the mirroritself, and it is this beat which causes the circuit to operate.

Going back to Fig. 3, consider first the case of the broken tungstenwire. If the mirror 28 is obscured by the flange 39, no light at allstrikes the photoelectric tube 38, therefore the triode of tube V1continues to pass just a slight D. C. current through the primary oftransformer T2 and because a transformer will pass from primary tosecondary only an alternating voltage, no voltage will appear at thesecondary of this transformer. On the other hand, if the mirror 28happens to be totally or partially in register with the opening 32 inthe flange 3B and is travelling at the same speed, a flash of light willstrike the phototube 38 with each revolution, but each flash will be ofequal intensity, and the frequency of these flashes will be equal to thespeed of the mirror and flange. These flashes will cause, as explainedbefore, the triode section of tube V1 to pass current through theprimary of transformer T2, and since the light is in the form offlashes, the current through the primary of transformer T2 will be inthe form of pulses at a frequency equal to the speed of the mirror.Transformer T2 will cause an A. C. voltage to appear across itssecondary winding and across potentiometer P2. Considering for a momentthat 6 the upper end of transformer T2 secondary is momentarilypositive, current will flow to the diode plate of tube V3 to cathode oftube V3, through resistance R5 and back to the other end ofpotentiometer P2. On the alternate half cycle when the upper end oftransformer T2 secondary is momentarily negative, due to therectification of the diode section of tubeVz no current will flowthrough resistance R5. A uni-directional current therefore flows throughresistance R5, and due to the filtering action of condenser C4 it issubstantially D. C. of polarity as indicated and its magnitude dependsupon the intensity of the light flashes. Since we are at the momentconsidering that the filament is broken and the flashes striking thephotoelectric tube 38 are all of equal intensity, a D. C. voltage ofconstant magnitude appears across resistance R5. Since the grid of thetriode section of. tube V3 is connected to the minus end of resistanceR5, the triode section of tube V3 may or may notbe passing plate currentthrough the primary of transformer T3 depending upon the magnitude ofthe equal light flashes. In any case, the voltage on the grid of tube V3is D. 0., therefore the plate current, if any, through the triodesection of this tube will be D. C. As before, a transformer will developa voltage across the secondary only if a varying current flows in itsprimary. In the case' under discussion, therefore, no voltage appears'across the secondary of transformer T3, andby the same reasoningapplied to the first or diode section of V4, Re, and C5 as was appliedto the diode section of .V3, R5, and C4, no voltage appears across R6.The grid of tube V4 has no biasing voltage on it, therefore, and itdraws plate current through and energizes the coil of relay 4U.Condenser Ce serves to filter out the supply frequency pulsations acrossthe coil of relay 40.

We have seen up to this point that if the tungsten filament is broken,there are two situations that can exist: First, the mirror 28 may becompletely obscured by the flange 30 so that no flashes at all reach thephototube. In this case no voltage appears across resistance R5, novoltage appears across resistance Re, and relay 40 is energized and itscontacts will be held open. Secondly, the mirror 28 may be onlypartially or not at all obscured by the flange 30 so that light flashesof constant magnitude strike the phototube, a steady D. C. voltage doesappear across R5, but no voltage can appear across Rs, so that againrelay 40 still remains energized with contacts open.

Consider now the case of the tungsten filament l8 not being broken andthe device being operated normally, a beat of comparatively lowfrequency strikes the phototube 38. This is due to the relatively smalldifference in speed of rotation of the mirror and the opening in theflange. The mirror 38 is uncovered by the opening 32 in the flange 30only after a large number of rotations of the mirror and flange. Avoltage will appear across R5 but it will not be aconstant. It will,rather, be a voltage whose magnitude varies with the beat frequency,since the time constant of R5 and C4 is insuflicient to filter this lowfrequency. The bias on the triode section of tube V3 will therefore varywith the beat frequency, current will flow in low frequency pulsesthrough the primary of transformer T3, and low frequency voltage pulseswill appear across the secondary of transformer T3 and will be rectifiedby the first (or diode) section of tube V4, and a voltage will appearacross Re. The values of Re and C are such as to give a time constantequal to or greater than this low frequency pulse, so a substantiallypure D. C. appears across Re. Sinceuthe grid of the triode section of V4is connected to the minus end of Re, it will be biased to cut-off, therelay will no longer be energized and the contacts for the motorcircuits will be closed, This is the case of the machinecontinuingtorun.

What I claim is:

1. A control for filament wrapping machines in which a filament carryingspool during normal operation rotates with and at a different speed fromguiding means therefor, an electronic circuit, a photoelectric tubetherein, a mirror-carried by said guiding means, a shield having anopening therein rotating with said spool whereby increasing anddecreasing light flashes are imposed on said photoelectric tube, saidphotoelectric tube receiving said variable flashes of light from saidmirror-during normal operation, and said circuit operating a relay tostop said machine when said flashes cease or become constant,

'2. A control for filament wrapping machines in which a :filamentcarrying spool rotates with and ata difierent speed from guiding meanstherefor during operation, an electronic circuit having a photoelectrictube therein, a mirror carried by one of said rotating means, a shieldhaving an opening therein carried by the other memher, saidphotoelectric tube receiving periodic variable flashes of light as saidmirror is variably uncovered by the opening in said shield at eachchine, and said circuit operating a relay to stop said machine when saidflashes cease or become constant.

3. A control for filament wrapping machines comprising, filament guidingmeans, rotating means for said guiding means, means to feed a core wireaxially of said guiding means, a spool rotatable with and relatively ofsaid guiding means, a mirror mounted for rotation with said guidingmeans, a flange rotatable with said spool having an opening thereinthrough which said mirror may be viewed during relative rotation of theshaft and spool, a light source, a. photoelectric tube positioned toreceive light from said source as reflected by said mirror, and anelectroniccircuit controlled by the flashes of light reflected by saidmirror upon said photoelectric tube for controlling operation of saidwrapping machine.

ALBERT M. DEXTER, JR.

REFERENCES CITED The following references are of'record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,971,191 Lord Aug. 21, 19342,101,382 Donovan Dec. 7, 1937 2,211,320 Efron Aug. 13, 1940 2,340,547Mikami Feb. -1, 1944 2,383,313 Hoffman Aug. 21, 1945 2,416,595 ReynoldsFeb. 25, 1947

